The Fighting Game community was better able to distill fighting games into simpler forms: see Divekick, a well respected, extremely simple 2-button fighting game. Its played on the following controller...
As it turns out, all the mechanics of fighting games can come down to this. Kara-cancels, footsies, space control, supers, etc. etc. It took a lot of effort for whoever made the game of Divekick, but its a fighting game in its simplest, and purest form.
This is NOT a beginner friendly game. In fact, Divekick is hugely punishing to beginners and I know my friends who have ragequit against me. Without careful practice, study, and understanding, a stronger player can absolutely overwhelm newer players in Divekick. There's a huge amount of knowledge: angles of attack, supers and other such details that make this game surprisingly difficult to get into. You know, like a fighting game.
A "simplification" of an RTS wouldn't dumb-down the mechanics or make them n00b friendly. "Simplification" would mean distilling the genre down to its essence, kind of like how Divekick did with fighting games.
Imagine if you will, an RTS with a singular unit, but all the controls of an RTS. With one unit, we only need one resource, and it can be collected automatically (without the need of SCVs / villagers / harvesters). Our upgrades can be resource-collection vs unit-production, and that's it.
This gives us rush vs tech builds (ex: no investment of economy at all, immediately attack the opponent). This gives us lanchester's square-law (12 units fight much stronger than 1-at-a-time), Lanchester's linear law (eventually the front saturates, and the quadratic-scaling of units dies out. Maybe 40 vs 40 plays out more linearly than one expects). Etc. etc.
This would be the "Divekick", but would beginners like the game? I doubt it, it would seem overly simple to beginners. And when an advanced RTS player kicks their ass even in "such a simple game", they'd swear off of the game... possibly the entire genre and never come back.
If you think about what draws people into RTS games, its almost always the campaign / story, with tutorial-level AIs that teach the mechanics step by step. The complexity of units is almost something a beginner can understand (while it'd take years of practice to understand positioning, timing attacks, build orders and the like).
Even the simplest game (ex: single unit RTS I described above) can be designed to have build orders, timing attacks, positioning, and other concepts that will allow an advanced player to utterly wipe out beginners. But this is not what they want, nor is it what will draw in players. It might still be worth building (like Divekick), as a celebration of the genre and as a overly-niche game for our tastes. But at no point should we confuse simplicity with beginner-friendliness.